Disclosed herein are photoinitiating compounds. More specifically, disclosed herein are photoinitiating compounds particularly compatible with or useful as compositions useful in curable phase change ink compositions. One embodiment is directed to a compound of the formula
wherein R1 is (i) an alkylene group, including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkylene groups, and wherein hetero atoms either may or may not be present in the alkylene group, (ii) an arylene group, including substituted and unsubstituted arylene groups, and wherein hetero atoms either may or may not be present in the arylene group, (iii) an arylalkylene group, including substituted and unsubstituted arylalkylene groups, wherein the alkyl portion of the arylalkylene group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkylene group, or (iv) an alkylarylene group, including substituted and unsubstituted alkylarylene groups, wherein the alkyl portion of the alkylarylene group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylarylene group, R2 and R2′ each, independently of the other, are (i) alkylene groups, including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkylene groups, and wherein hetero atoms either may or may not be present in the alkylene group, (ii) arylene groups, including substituted and unsubstituted arylene groups, and wherein hetero atoms either may or may not be present in the arylene group, (iii) arylalkylene groups, including substituted and unsubstituted arylalkylene groups, wherein the alkyl portion of the arylalkylene group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkylene group, or (iv) alkylarylene groups, including substituted and unsubstituted alkylarylene groups, wherein the alkyl portion of the alkylarylene group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylarylene group, R3 and R3′ each, independently of the other, are either (a) photoinitiating groups, or (b) groups which are (i) alkyl groups, including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkyl groups, and wherein hetero atoms either may or may not be present in the alkyl group, (ii) aryl groups, including substituted and unsubstituted aryl groups, wherein hetero atoms either may or may not be present in the aryl group, (iii) arylalkyl groups, including substituted and unsubstituted arylalkyl groups, wherein the alkyl portion of the arylalkyl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkyl group, or (iv) alkylaryl groups, including substituted and unsubstituted alkylaryl groups, wherein the alkyl portion of the alkylaryl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylaryl group, provided that at least one of R3 and R3′ is a photoinitiating group, and X and X′ each, independently of the other, is an oxygen atom or a group of the formula —NR4—, wherein R4 is (i) a hydrogen atom, (ii) an alkyl group, including linear and branched, saturated and unsaturated, cyclic and acyclic, and substituted and unsubstituted alkyl groups, and wherein hetero atoms either may or may not be present in the alkyl group, (iii) an aryl group, including substituted and unsubstituted aryl groups, and wherein hetero atoms either may or may not be present in the aryl group, (iv) an arylalkyl group, including substituted and unsubstituted arylalkyl groups, wherein the alkyl portion of the arylalkyl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the arylalkyl group, or (v) an alkylaryl group, including substituted and unsubstituted alkylaryl groups, wherein the alkyl portion of the alkylaryl group can be linear or branched, saturated or unsaturated, and cyclic or acyclic, and wherein hetero atoms either may or may not be present in either the aryl or the alkyl portion of the alkylaryl group.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labelling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 5,804,671 (Dones et al.), the disclosure of which is totally incorporated herein by reference, discloses a composition that is useful in the preparation of radiation curable coatings. The composition comprises the reaction product of an epoxy component comprising a diepoxide and an acid component comprising an ethylenically unsaturated carboxylic acid or reactive derivative thereof, reacted in the presence of a polyamide based on a polymerized fatty acid. The polyamide preferably has a number average molecular weight of less than about 10,000 g/mole. Also provided is a polymerizable composition comprising the reaction product and a reactive diluent. A method of coating a substrate is also provided which comprises applying to a substrate a composition comprising the reaction product and exposing said composition to radiation to cure said composition.
U.S. Pat. No. 5,889,076 (Dones et al.), the disclosure of which is totally incorporated herein by reference, discloses a composition that is useful in the preparation of radiation curable coatings. The composition comprises the reaction product of an epoxy component and an acid component comprising an ethylenically unsaturated carboxylic acid or reactive derivative thereof, reacted in the presence of, or post-reaction blended with, a polyamide based on a polymerized fatty acid. The polyamide preferably has a number average molecular weight of less than about 10,000 g/mole. Also provided is a polymerizable composition comprising the reaction product, the polyamide, and a reactive diluent. A method of coating a substrate is also provided which comprises applying to a substrate a composition comprising the reaction product and the polyamide and exposing said composition to radiation to cure said composition.
U.S. Pat. No. 6,239,189 (Narayan et al.), the disclosure of which is totally incorporated herein by reference, discloses a radiation-polymerizable composition containing at least one radiation curable acrylate resin oligomer prepared by reacting an alkoxylated polyol with a first acid component which includes an ethylenically unsaturated carboxylic acid, and a rheology modifier prepared by reacting a diepoxide with a second acid component which includes an ethylenically unsaturated carboxylic acid or reactive derivative thereof in the presence of a polyamide based on a polymerized fatty acid. The ethylenically unsaturated carboxylic acids of the first and second acid components are preferably acrylic acid or methacrylic acids. The diepoxide is preferably a diglycidyl ether such as bisphenol A. Colorants such as pigments or dyes optionally may be incorporated into the composition to form a printing ink which is curable by ultraviolet (UV) or electron beam radiation.
U.S. Pat. No. 6,316,517 (Dones et al.), the disclosure of which is totally incorporated herein by reference, discloses radiation-polymerizable compositions especially useful as or in a flush vehicle for making flushed pigments. The compositions contain at least one radiation-curable acrylated resin component and a copolymerizable rheology modifier component.
U.S. Patent Publication 2003/0036587 (Kozak), the disclosure of which is totally incorporated herein by reference, discloses rheology-controlled epoxy-based compositions particularly well suited for use in coating applications such as in the assembly of ink jet printheads for the printing industry, and in the microelectronics industry such as in the assembly of semiconductor devices.
U.S. Pat. No. 6,586,492 (Caiger et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink-jet ink including an ink jet vehicle and a colorant. The vehicle includes at least 35 percent by weight radiation curable material based on the total vehicle weight. The vehicle may but does not necessarily include a thickener. The vehicle is a paste or a solid at 20° C. and has a viscosity of less than 25 centipoise between 40° C. and 130° C.
U.S. Pat. No. 6,467,897 (Wu et al.), the disclosure of which is totally incorporated herein by reference, discloses compositions that incorporate surface modified, nanometer sized, inorganic oxide particles into energy curable fluids. The surface modification aspect allows the compatibility between the particles and fluid to be controllably adjusted to achieve a wide range of rheological characteristics. For printing, preferred compositions have favorable dot gain and thickness build up. When the composition is cured, the presence of the particles also helps improve physical properties such as hardness, modulus, abrasion resistance, refractive index, and the like. The compositions are particularly well-suited for forming printed, radiation cured features on substrates such as paper, signs, walkways, roadways, motor vehicles, boats, aircraft, furniture, equipment, and the like.
U.S. Pat. No. 6,896,937 (Woudenberg), the disclosure of which is totally incorporated herein by reference, discloses radiation-curable ink compositions and methods of printing including the compositions. In some embodiments, a radiation-curable hot melt ink composition includes a colorant, a polymerizable monomer, and a photoinitiating system. The photoinitiating system can include 0.5 to 1.5 percent by weight of an aromatic ketone photoinitiator, 2 to 10 percent by weight of an amine synergist, 3 to 8 percent by weight of an alpha-cleavage type photoinitiator, and 0.5 to 1.5 percent by weight of a photosensitizer.
While known compositions and processes are suitable for their intended purposes, a need remains for improved photoinitiators. In addition, a need remains for improved phase change inks. Further, a need remains for photoinitiators that are soluble in, miscible in, or otherwise compatible with phase change ink vehicles. Additionally, a need remains for photoinitiators that lead to reduced odor when used in curable phase change inks prior to curing. There is also a need for photoinitiators that lead to reduced odor when used in curable phase change inks subsequent to curing. In addition, there is a need for photoinitiators that lead to reduced surface yellowing in images when used in curable phase change inks. Further, there is a need for photoinitiators that exhibit reduced migration through cured images when used in curable phase change inks. Additionally, there is a need for photoinitiators having improved affinity for phase change inks exhibiting a gel phase during the printing process. A need also remains for a photoinitiator having reduced volatility in itself and also having reduced volatility of its fragments. In addition, a need remains for photoinitiators that in themselves exhibit gellant characteristics. Further, a need remains for photoinitiators that have improved affinity for the ordered microstructure of the gel phase, as opposed to being excluded from that order. Additionally, a need remains for photoinitiators that are themselves curable.